CA1087787A

CA1087787A - Brake lining compositions having friction particles of an aromatic acmine modified novalac resin and an aromatic carboxylic compound

Info

Publication number: CA1087787A
Application number: CA289,405A
Authority: CA
Inventors: Philip H. Brodsky
Original assignee: Monsanto Co
Current assignee: Solutia Inc
Priority date: 1976-10-26
Filing date: 1977-10-25
Publication date: 1980-10-14
Also published as: GB1559242A; AU512138B2; US4101500A; AU3001177A

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention relates to a brake lining composition comprising friction particles and a resin binder therefor, said friction particles being a thermoset reaction product of an amine modified novolac resin and an aromatic polycarboxylic compound having improved thermal stability. The invention also relates to a method for preparing said brake lining composition.

Description

C-06-12-0430 108~87 BRAKE LINING COMPOSITIONS HAVING FRICTION PARTICLES
OF AN AROMATIC AMINE MODIFIED NOVOLAC RESIN
- --AND AN AROMATIC CARBOXYLIC COMPOUND
BACKGROUND OF THE INVENTION
This invention relates to novel cured phenolic resins to be used as a friction particle material. It is especially use-ful where cashew nut shell oil friction particles, called "Cardolite" have been used in the past.
Novolac phenol aldehyde resins are phenol-ended chain 1~ polymers. They are formed by the reaction of an aldehyde with an excess of phenol in the presence of an acid catalyst and/or heat. They are thermoplastic, permanently soluble and fusible.
However, upon the addition of a curing agent, they can be cured into an insoluble, infusible resin. Thus, novolac resins are known as "two-stage" resins.
Phenol aldehyde condensation products have been used as binders for abrasive materials. However, to our knowledge, the novel cured phenol aldehyde products of this invention have not been used as a friction particle per se.

2~As used herein "friction particle" is intended to mean having the properties of substantially nO softening at elevated tempe~atures and will not flow together or cohere with other particles, as a "friction binder" would, or fuse with like friction particles. It is insoluble, having an acetone extrac-tion of less than 10% and often less than 5~; it is infusible, i.e., has gone beyond the B stage, to the C stage. It will not melt at 700 degrees Fahrenheit. A friction particle is held in place with a friction binder.
As used herein, a "friction binder" has the properties of flowability, and has adhesive and cohesive bonding action and *Trade Mark 108778~ .

thereby binds together the asbestos and other additives (in-cluding a friction particle) necessary for building a brake lining or other similar article of manufacture. The binder, as ~~
supplied to the industry, will melt as a dry powder or is a liquid resin, and can be either an A stage or B stage resin.
The binder becomes a C stage resin after it is combined with the other ingredients and cured.
This composition of the binder, friction particle and other additives, is heated to about 300-400 Fahrenheit and pressed at about 500-2000 pounds per square inch in order to form a brake lining composition, or clutch facing or other brak-ing device. Thus, the friction particle is substantially in-soluble and infusible, softening only at elevated temperatures (i.e., above about 400-500 Fahrenheit). Conventional "two stage phenolic novolac resin can be used as a binder in the composition of the present invention.
It has now been found that a composition of matter, use-ful as a friction particle, can be prepared as a reaction prod-uct of an aromatic amine modified novolac resin cured in com-bination with a particular aromatic polycarboxylic compound.The friction particles have superior high temperature properties in brake lining compositions. Friction particles prepared from polymerized cashew nut shell liquids, known as Cardolites, are commonly used as friction particles but fade (loss of coefficient of friction) at temperatures as low as 700-800F. Substitution of the friction particles of the present invention extend the onset of fade from about 750F. to about 1000F. giving high utility in brake lining compositions and providing a recognized technical advance in the art in compositions having, e.g., about 10877~7 15 to 30% by weight of phenolic novolac resin binder, about 30 to 60% by weight of asbestos, up to about 40~ by weight of fillers and about 5 to 15~ by weight of friction particles.
SUMMARY OF THE INVENTION
The present invention relates to a novel brake lining composition comprising friction particles and a resin binder therefor,said friction particles comprising a thermoset reaction product of (A) an aromatic amine modified novolac resin characterized by having (1) a number average molecular weight of from about 200 to 1000, (2) at least two aryl moieties per molecule, the aryl nucleus of each aryl moiety containing from 6 through 10 carbons atoms each,

(3) at least one divalent bridging moiety of the formula:
.

I 1 .
f wherein R and R are each individuall selected from the group consisting of hydrogen, lower alkyl, lower alkalene, lower haloalkyl aryl of from 6 through 12 carbon atoms and haloaryl of 6 through 12 carbon atoms, said bridging moiety having the unsatisified valences of its carbon atom each bonded to a different one of said aryl moieties,

(4) at least one ~ NH group per molecule, one bond of which is directly S attached to one of said aryl nuclei and the other bond of which is attached to another of said aryl nuclei or to a radical Rl as defined above,

(5) at least one OH group per molecule each such group being directly attached to a different one of said two aryl nuclei,

(6) a percent oxygen acetyl of from about 3 to 26, and

(7) a percent nitrogen acetyl of from about 3 to 26, and (B) an aromatic polycarboxylic compound of the formula:
r 1l~0l -R3 ~ / (-COO~)m(-COOR4)p L _ n in which R3 is an aromatic radical of three, four, five or six valences and containing from 6 to 24 carbon atoms, R4 is a monovalent hydrocarbon radical containing less than 19 C-06-12-04~0 108~87 carbon atoms; n is an integer of from 0 through 3; m is an integer of from 0 through 6; p is an integer of from 0 --through 6; when n is 0, the sum of s m+p is an integer of from ~ through 6;
when n is 1, the sum of m+p is an in-teger of from 1 through 4; when n is 2, the sum of mlp is an integer of from 0 through 2; and the sum of n and p is always at least 1, (C) the relative proportions of said amine modified resin and said aromatic poly-carboxylic compound being such that said composition is thermoset by heat.
lS ~he invention also relates to a novel method of forming a brake lining composition comprising the blending of a resin binder, friction particles and additives wherein the improvement comprises, the blending of friction particles comprising a thermoset reaction product of:
(A) an aromatic amine modified novolac resin characterized by having:
(1) a number average mole~ular weight of from about 200 to 1000, (2) at least two aryl moieties per molecule, the aryl nucleus of each aryl moiety containing from 6 through 10 carbon atoms each, (3) at least one divalent bridging moiety of the formula:

C-06-12-0430 108~87 --C

wherein Rl and R2 are each individually selected from the group consisting of hydrogen, lower alkyl, lower alkalene, lower haloalkyl aryl of from 6 through 12 carbon atoms and haloaryl of 6 through 12 carbon atoms, said bridging moiety having the unsatisfied valences of its carbon atom each bonded to a different one of said aryl moieties, (4) at least one ~ NH group per molecule, one bond of which is directly attached to one of said aryl nuclei and the other bond of which is attached to lS another of said aryl nuclei or to :
a radical Rl as defined above, (5) at least one OH group per molecule each such group being directly attached to a different one of said two aryl nuclei, (6) a percent oxygen acetyl of from about 3 to 26, and (7~ a percent nitrogen acetyl of from about 3 to 26, and (B) an aromatic polycarboxylic compound of the formula:

C-0~-12-0430 ll . ~

R3 ~ I / (-COOH)m(-COOR4)p _ O _ n in which R3 is an aromatic radical of three, four, five or six valences and con-taining from 6 to 24 carbon atoms, R4 is a monovalent hydrocarbon radical containing less than 19 carbon atoms; n is an integer of from 0 through 3; m is an integer of from 0 through 6; p is an integer of from 0 through 6; when n is O, the sum of m~p is an integer of from 3 through 6; when n is 1, the sum of m+p is an integer of from 1 through 4; when n is 2, the sum of m~p is an integer of from 0 through 2; and the sum of n and p is always at least 1, (C) the relative proportions of said amine modified resin and said aromatic poly-carboxylic compound being such that said composition is thermoset by heat.
. PREFERRED EMBODIMENTS
NOVOLAC BINDERS
The binder resin can be conventional preformed two stage phenolic-formaldehyde novolac resins~ Procedures for preparation of such resins are disclosed in the publication, "Polymer Processes" by C. E. Schildknicht, Interscience Pub-lishers Inc., New York, New York (1956), page 315. The methods of making such preformed novolac resins are well known to those skilled in the art and do not constitute a part of the inven-tion. A preferred novolac binder resin has been disclosed in U. S. P. 3,538,052 by H. P. Higginbottom as a post-al~ylated novolac resin wherein the alkylating materials are a mixture of arylalkenes, arylcycloalkenes, dicyclopentadienes and cyclo-pentadiene/acylic conjugated diene codimers.
In general, these post-alkylated novolacs are made using preformed novolacs as starting materials. Such preformed novolacs are conventionally made, as by first reacting from about 0.4 to 0.g5 mol of aldehyde per mol of phenol under acidic cata-lyzed aqueous phase reaction conditions until a condensation product of aldehyde with phenol having desired characteristics is produced. .
The term "phenol" and the term "aldehyde" each have established meanings of ScOpe in the art of phenolic resins and are used throughout this disclosure and claims in accordance with their generic art established meanings. Thus, the term "phenol" refers to an aromatic six-membered moiety which is substituted with a hydroxyl group. This moiety can be further substituted with other radicals including alkyl radicals, aryl radicals, halo radicals, (including fluorine, chlorine, bromine and iodine), hydroxyl groups and the like as those skilled in the art fully appreciate. A preferred phenol is phenol itself.
Similarly, the term "aldehydel' has reference to organic com-pounds containing the characteristic group:

108778'7 Examples of suitable aldehyes known to the phenol-aldehyde resin art include aliphatic aldehydes, such as propionaldehyde, acetaldehyde and the like; aromatic aldehydes such as benzalde-hyde and the liXe, cyclic aldehydes such as furfural and the-like and mixtures of such. A preferred aldehyde is formalde-hyde.
A preferred procedure for making a preformed novolac starting resin involves refluxing aldehyde and phenol in the afore-indicated mol ratios under aqueous phase conditions with - an acidic catalytic material such as sulphuric acid, phosphoric acid, oxalic acid and the like, for a time of from about 20-140 minutes. Then the mixture is dehydrated under vacuum to about 120-160C. and cooled to produce a solid product.
It will be appreciated that the aldehyde to phenol ratios herein described have reference to the total amount of phenol present before a reaction, including the phenol which is substituted.
Such a preformed novolac resin starting material can be reacted with a controlled mixture of arylalkenes, aryl-cycloalkenes, dicyclopentadienes and cyclopentadiene/acylic conjugated diene codimers herein termed the diene codimer mix-ture which comprises a form substantially free of other materials.
Such a starting material diene codimer compound mixture can be prepared synthetically or derived by suitable preparative procedures from naturally occurring crude petroleum, as those skilled in the art will appreciate. A preferred mixture of such diene codimer compounds for use in this invention is a petroleum derived blend of components having diluents already incorporated thereinto. For example, one suitable such mixture is available commercially under the trade designation "Resin Former P" from the Hess Oil and Chemical Company.
To react a preformed novolac with such an aforedescribed diene codimer compound mixture, it is convenient to use Friedel-Crafts conditions. r The term "Friedel-Crafts conditions" as used herein re-fers to the conventional conditions known to those of ordinary skill in the art used for the alkylating or arylating of hydro-carbons (including phenol) by the catalytic action of aluminum chloride or equivalent catalyst in the presence of appropriate heat and pressure. Conveniently, the preformed novolac and suitable Friedel-Crafts acid catalyst are mixed, brought to the proper temperature and the,diene codimer mixture metered into the acidified (or catalyzed) preformed novolac.
For purposes of this invention, the reaction with pre-formed novolac is preferably carried out at temperatures in the range of from about 25 to 200C., although higher and lower temperatures can be used. Also, the reaction is preferably con-ducted under liquid phase conditions at or below atmosphere pressures although superatmospheric pressures can be used. In-ert hydrocarbons, as indicated above, generally facilitate the process. Such inert hydrocarbons can be readily removed, such as by vacuum stripping, at the completion of the reaction if de-sired. Especially when stripping is contemplated, the most pre-ferred inert hydrocarbons have boiling points between about 70 and 140C. The progress of the reaction can be monitored, if desired, by measuring the quantity remaining of unreacted diene S codimer compound using, for example, vapor phase chromoatography.
While any combination of diene codimer compound starting mixture, preformed novolac and catalyst can be used, it is par-ticularly convenient to react for each lO0 parts by weight of starting preformed novolac about 5 to 100 by weight parts of such diene codimer compound mixture in the presence of less than about lO weight percent (based on the preformed novolac) of acid catalyst. Preferably from 0.1 to l.0 weight percent of acid catalyst is used.
The reaction mass is then heated to a temperature in the range of from about 25 to 200C. The rate of this reaction is dependent, to some degree, on the temperature employed. In gen-eral, the reaction is rapid, and a complete reaction between preformed novolac and diene codimer compound mixture is pre-ferred. For the purpose of insuring complete reaction, gener-ally a heating time of from about lO minutes to 4 hours is em-ployed.
The properties (e.g., molecular weight distribution, color and the like) of a given so-substituted novolac product are affected by the process conditions used to make that prod-uct. The resulting reaction product is as those skilled in theart will appreciate, a complex mixture of various different sub-stituted phenols produced from the reaction of novolac under Friedel-Crafts conditions with diene codimer compound starting mixture to produce novolac molecules which are substituted both 108~787 on phenyl ring carbon atoms and on phenyl hydroxyl oxygen atoms by moieties derived from such diene codimer compound mixture.
The novolac resins of this inVentiOn before use are typically formulated with a curing agent in order to produce a thermosettable composition. Although any conventional novolac curing agent can be used, it is preferred to employ those which are substantially nonvolatile at room temperatures and pres- r sures.
The curing agent employed herein can be hexamethylene-tetramine; an epoxy compound containing the group:

O\
CH2 CH CH2; or the like.

However, in the preferred practice of this invention, hexa-methylenetetramine is employed as the curing agent.
Although liquid curing agents can be used in the prac-tice of this invention, particulate solid curing agents are preferred.
Preferably, when the curing agent is such a solid, it has an average ~maximum dimension) particle size of less than about 100 microns. Initially, at the time of admixing, it is preferably, though not necessarily, in a finely divided form (i.e., under about 44 microns in maximum average dimension, and more preferably under about 100 microns).
Mixing of curing agent with novolac can be accomplished by any conventional means, such as by physically intermixing a powdered novolac with the curing agent until a uniform composi-tion is obtained.
The thermosetting novolac resin and curing agent compo-sitions comprise from about 3 to 25 parts by weight of curing agent per 100 parts by weight of substituted phenol-aldehyde novolac. Preferably, th~ amount of curing agent present in ~~
these compositions ranges from about 10 to 20 parts by weight per 100 parts by weight of novolac resin.
It may be desirable to also incorporate conventional materials with the powdered, solid phenolaldehyde novolac and the curing agent. This includes, for example, such materials as powdered rubber, linseed oil, magnesium silicate, calcium 1~ carbonate, barytes, talc, clay, finely divided asbestos fibers, pigments having tinctorial properties and glass fibers. The amount of these fillers can vary depending upon the desired end application or use of the resin. They may be first added to the novolac during the preparation thereof or they may be added during the preparation of the composition of novolac and curing agent.
This product is useful as an adhesive and binder for particulate materials. In general, the novolac resins in powder form find use in all applications known to the prior 0 art where thermosetting powdered resins are used.
FRICTION PARTICLES
Heretofore, those skilled in the art of phenolic resins have long appreciated that such resins, especially those of the novolac type, have their thermosetting character enhanced or promoted through the use of curing agents, such as hexamet~lyl-1087~87 enetetramine, and the like. The art has long sought to improve the characteristics of cured (crosslinked) thermosettable phenolic resins through varying either or both the chemical com-positions and amounts, respectively, of phenolic resin and cur-ing agent employed in any given instance.
One of the characteristics of thermoset phenolic resins which has been particularly difficult to improve has been that of thermal stability, such as the ability of a particular ther-moset phenolic resin to withstand, and be stable to, prolonged exposure to elevated temperature. Such thermal stability can be measured by any convenient means, such as by thermal gravimetric analysis, or by strength retension measurements (or weight loss measurements) of standardized laminate constructions (contain-ing a given thermoset phenolic resin to be tested).
Such difficulties in improving thermal stability, recent evaluations have apparently shown, are probably inherently caused by.the structural limitations in three-dimensional cross-linked phenolic resins. A cured phenolic resin does not heat soften or change dimensions upon heat exposure but instead tends to degrade and lose structural integrity once an inherent thresh-old temperature (typically, about 450F.) has been exceeded for an appreciable period of time.
A new and much improved class of thermoset phenolic resins has now been discovered. This class comprises a thermo-settable mixture of amine modified novolac resins and aromaticpolycarboxylic compounds. When compared with conventional novolacs conventionally cured (as with hexamethylenetetramine), this new class of phenolic resins has surprising thermal sta-bility when thermoset. This improvement in thermal stability is, it is theorized (and there is no intent to be bound by theory herein), a result of the increased structural strength on a molecular crosslinking basis associated with these new phenolic --resins.
The present invention relates to new and useful thermo-set phenolic resin compositions of matter, to thermoset composi-tions produced therefrom, and to articles of manufacture incor-porating such compositions. In relation to comparable prior art phenolic resin compositions, these new compositions generally have improved thermostability as thermoset.
The thermoset compositions of this invention comprise at least one amine modified novolac phenolic resin and at least one aromatic polycarboxylic compound. Such an amine modified novolac resin is generally characterized by having:
(1) A number average molecular weight of from about 200 to 1000, (2) At least two aryl moieties per molecule, the aryl nucleus of each aryl moiety containing from 6 through 10 carbon atoms each, (3) At least one divalent bridging moiety of the formula:

f wherein Rl and R2 are each individually selected from the group consisting of hydrogen lower alkyl, lower alkalene, lower haloalkyl, aryl of from 6 through 12 carbon atoms, haloaryl of 6 through 12 ~087787 carbon atoms, and heterocyclic structures con-taining rings with 5 or 6 members each, each individual ring containing an oxygen, a sulphur, --or a nitrogen atom, each such heterocyclic structure being bonded to the carbon atom of said bridging moiety, said bridging moiety having the unsatisfied valences of its carbon atom each bonded to a different one of said aryl moieties, (4) At least one ~ NH group per molecule one bond of which is directly attached to one of said aryl nuclei and the other bond of which is attached to another of said aryl nuclei or to a radical Rl as defined above, (5) At least one OH group per molecule each such group being directly attached to a different one 4f said two aryl nuclei, (6) A percent oxygen acetyl of from about 3 to 26, and (7) A percent nitrogen acetyl of from about 3 to 26. Similarly, such an aromatic polycarboxylic compound is characterized as being within the given class of compounds having the general formula:

~0877B7 R3 ~ ~ (-COOH~m(-COOR4)p in which R3 is an aromatic radical of three, four, five or six valences and containing from 6 to 24 carbon atoms, R4 is a monovalent hydro-carbon radical containing less than 19 carbon atoms; n is an integer of from 0 through 3; m is an integer of from 0 through 6; p is an in-teger of from 0 through 6; when n is 0, the sum of m~p is an integer of from 3 through 6, when n is 1, the sum of m+p is an integer of from 1 through 4; when n is 2, the sum of m+p is an integer of from 0 through 2; and the sum of n and p is always at least 1.
Preferably, Rl and R2 are both hydroben, R3 contains a single six membered aromatic ring (i.e., phenyl), and R4 is a lower alkyl radical. The term "lower" as used herein refers to a radical containing less than seven carbon atoms.
In general, in any given composition of this invention, there is present for a given amount of such amine modified novolac resin, at least sufficient amount of such aromatic polycarboxylic compound to make the resulting composition thermosettable by heat alone (especially when such composition is in the form of a uniform mixture of the respective two com-ponents); for example, at a temperature of about 150C.

In general, thermosetting of a thermoset resin composi-tion of this invention results from the reaction of an aromatic polycarboxylic compound with the reactable aromatic amine and -the reactable aromatic hydroxyl group in an amine modified novolac starting material. Sometimes as little as about 5 or 10 weight percent (or even less) of the stoichiometric amount (that is, the amount of dicarboxyl compound) needed to com-pletely react on a 1:1 mol basis each reactable aromatic amine group plus each reactable aromatic hydroxyl group with dicar-boxyl compound is sufficient to effect thermosetting. On theother hand, sometimes as much as a 100% excess (or even more) of the stoichiometric amount as just described of dicarboxyl compound is desirable in a composition of the invention to pro-duce thermosetting of a composition of this invention. Prefer-ably, from about 80 to 110 weight percent of such stoichio-metric amount is employed.
For purposes of this invention, the term "thermoset" in reference to compositions of this invention indicates that a given thermosettable composition, after exposure to elevated temperatures for times sufficient to substantially completely react together substantially all of one of the two components (depending upon which one is present in excess of stoichiometric amount) with the other component comprising a composition of this invention so as to produce a product which is not only substantially insoluble, but also is substantially infusible.
For purposes of this invention, the term "substantially insolu-ble" in relation to "thermoset" has reference to insolubility in common organic solvents, such as methyl ethyl ketone, so that not more than about 10 weight per-1087~87 cent of a given so thermoset product dissolves in such a sol-vent Similarly, the term "substantially infusible" has refer-ence to the fact that a given or thermoset product does not ~~
appreciably melt before decomposing when heating to elevated temperatures.
Because of the tendency for undesirable side reac~ions to occur and because of the possibility that the thermosettable compositions of this invention will not uniformly crosslink in the presence of appreciable amounts of moisture, the thermo-settable compositions of this invention are prepared using amine modified novolacs and aromatic polycarboxylic compounds, re-spectively, in substantially anhydrous form. The term "sub-stantially anhydrous" has reference to the fact that a given material contains initially less than about 5 weight percent free water (based on total weight) and preferably less than about 1 weight percent thereof and most preferably less than about 1/2 weight percent thereof.
THE AMINE MODIFIED NOVOLAC
STARTING MATERIAL
In general, any amine modified novolac resin known to the prior art having the above-described characteristics can be used in the compositions of this invention. Because of possi-ble ambiguities in prior art teachings relating to production of amine modified novolacs, a brief discussion of the prepara-tion and properties thereof are now given.
For purposes of this invention, "oxygen acetyl percent"
of an amine modified novolac is conveniently determined by the method of Stroh and Liehr, J. Prakt. Chem. 29 (1-2), H. (1965).
Similarly, for purposes of this invention, "total acetyl C-0~-12-0430 percent" of an amine modified novolac is conveniently determined by the method of Siggia. Nitrogen acetyl percent is obtained by difference. ~~
Typical beginning materials suitable for use in making amine modified novolac resins are:
(A) A phenol which has at least one unsubstituted reactive position on the aromatic nucleus, (B) An aromatic amine which has at least one primary amine group or at least one secondary amine group substituted on an aromatic nucleus, and (C) An aldehyde containing at least one aldehyde group.
The phenols which can be employed in this invention are aromatic alcohols which have at least one hydroxyl group directly attached to the aromatic nucleus and which have at least one unsubstituted reactive position on the aromatic nu-cleus. It is normally the case that the reactive positions on the aromatic nucleus are those which are ortho and para to the hydroxyl group. Therefore, phenols which have at least one un-substituted position ortho or para to the hydroxyl group are particularly useful.
Preferred phenols are phenol itself, alkylphenols, and aryl phenols wherein substituents on this phenol benzene ring have a total of from 1 to 8 carbon atoms, and most preferably, from 1 to 6 carbon atoms.
The aromatic starting amines which can be employed can be of many different types. Thus, it can be a class represented by the formula:

C-06-12-0430 1~87 ArNH2 wherein Ar is an aryl group which has at least one unsubstituted reactive position on the aromatic nucleus. It can also be a class represented by the formula:

NH

wherein Ar is as just defined and R5 is an alkyl radical, an aralkyl radical, an alkaryl radical, or the like. Preferably, Ar is a phenyl radical and R5 contains less than 11 carbon atoms.
Ordinarly, the reactive positions are those which are ortho and para to the amino group. Accordingly, aromatic amines which have at least one unsubstituted position ortho or para to the amino group are preferred for use in preparing the condensation products employed in the invention. The presently most preferred aromatic amines are aniline, the alkyl-substi-tuted anilines wherein the alkyl groups thereof have from 1 to 4 ~arbon atoms, and the alkyl-substituted diaminobenzenes wherein the al~yl groups thereof have from 1 to 4 carbon atoms.
The amines operative in the present invention can be aromatic diamines. Both aromatic primary and secondary di-amines are operative in the present invention, but the aromatic primary diamines are preferred over the secondary because the secondary diamines are less desirable as the thermal stability and hydrolytic stability are apparently less than the primary diamines. The diamines are of the general formula:

.

wherein R6 is a divalent aromatic radical. Also operative are aromatic diamines having the general formula:

wherein R6 is as above defined and R7 is an alkyl radical, an aryl radical, an aralkyl radical, an alkaryl radical, or the like. Preferably, R6 is a phenyl radical and R7 is a lower alkyl radical.
The aldehydes which can be employed are alkanals such as formaldehyde, acetaldehyde, propionaldehyde and the like, arylals such as benzaldehyde, salicylaldehyde, and the like, haloalkanols, such as chloral, and the like. Formaldehyde is preferred. The formaldehyde can be employed in water solution or dispersion, or in an organic solvent such as methanol. It is ' preferred to employ the formaldehyde in aqueous solution (such as the 37 weight percent aqueous solution known as formalin).
Paraform can also be used.
Sometimes, if desired, the phenol and the aromatic amine can be combined into a single starting compound wherein the same aromatic nucleus has substituted thereon at least one hydroxyl group and at least one primary or secondary amine group. Simi-larly, if desired, the phenol and the aldehyde can be combined into a single starting compound wherein the same aromatic nu-cleus has substituted thereon at least one aldehyde group and at least one hydroxyl group. Similarly, if desired, the aro-matic amine and the aldehyde can be combined into a single 1087~787 starting compound wherein the same aromatic nucleus has substi-tuted thereon at least one aldehyde group and at least One pri-mary or secondary amine group. ~
When such a composite polyfunctional starting material is employed, it is preferred to use such in admixture with an aromatic amine, a phenol and an aldehyde. For example, one could employ up to about 50 weight percent of such a polyfunc-tional material in making an amine modified novolac.
When one makes an amine modified novolac resin using, for example, a phenol, an aromatic amine and an aldehyde, it is convenient and preferred to condense the starting materials under aqueous liquid phase conditions using heat and an acid catalyst. Conventional and preferred acid catalysts are or-ganic carboxylic acids (mono or polybasic) which are relatively strong as respects their disassociation constants. Examples of suitable such acid catalysts include: aliphatic carboxylic acids, such as formic, propionic, oxalic, diglycolic, fumaric, itaconic, lactic, maleic, malonic and the like and aromatic mono and dicarboxylic acids, such as naphthoic, phthalic, sali-cyclic, and the like.
The amount of acid catalyst employed can vary but in general is sufficient to produce a pH in an aqueous liquid phase medium of from about 1.5 to 6.0 (preferably from about 2.0-4.0) but this is not necessarily a critical factor.
The proportion of reactants employed is likewise not necessarily a critical factor and can be varied over a wide range. For example, the mol ratio of aromatic amine groups to phenolic -OH groups ranges from about 90/1 to l/90 and the mol ratio of aldehyde to the sum of aromatic amine groups plus phenolic -OH g~oups ranges from about 0.5 to 0.99. For in-stance, in a preferred specific embodiment, the charged mol ratio of aniline to phenol can range from about 95:5 to 5:95, though a --more preferred range is from ab~out 1:1 to 9:1. Sufficiently, and for example, the charged mol ratio of formaldehyde to the sum total of aniline and phenol is less than about 1:1. In general, the higher the aniline content, the higher the formaldehyde to combined aniline and phenol mol ratio can be without a generally undesirable gelation (because gelation substantially prevents post-working) occurring as a side phenomenon during condensation.
To avoid gelation in ma~ing such a preferred embodiment, the following relationships can be used as guides:

TABLE I
Use-Formaldehyde At-Aniline/phenol to aniline plus mol ratio phenol mol ratio 1:1 - - - - - - - - Smaller than ~.70:1.
90:10 - - - - - - - - Smaller than 0.95:1.
60:40 - - - - - - - - Smaller than 0.75:1 80:20 - - - - - - - - Smaller than 0.80:1.

For such a condensation, the acid catalyst is preferably formic acid, oxalic acid, or propionic acid in an amount of from about 0.5 to 5 parts catalyst per 100 parts phenol (by weight).
The temperature of reactants in such preferred emobdiment can vary from about 60 to 100C. Agitation of reactions during con-densation is preferably continuous. It is not necessary for the reactants to be charged together to a reactor thus, formaldehyde can be slowly added to a warmed mixture of aniline, phenol and acid catalyst. The entire condensation may be carried out at re-flux temperatures if desired. Since a co-condensation reaction is apparently involved, the reaction mechanism, it is theorized, ~0877~7 may involve formation of low molecular weight intermediates which initially form, and then possibly rearrange and combine with one another at a later stage. Typically, condensation re- --action conditions are maintained until all aldehyde is consumed.
In general, conventional equipment can be employed for the condensation reaction. For example, a reaction kettle equipped with agitator, means for reflux and distillation, ni-trogen inlet means, and conventional heat transfer means is suitable. The material of construction can be steel, stainless Steel~ glass, Monel, or the like.
In general, a preferred method for carrying out the condensation reaction of the phenol, aldehyde and amine starting materials is to add the aldehyde slowly to an agitated mixture of phenol and aromatic amine containing the acid catalyst. This mixture is maintained at a temperature of from about 50C. to about 125C., and preferably from about 70C. to about 105C.
during the addition. After the addition of aldehyde, which can take from about one hour to about four hours or longer, the con-densation reaction is continued for about 30 minutes to about 3 hours at a reaction temperature of from about 50C. to about 125C., and preferably, from about 95C. to about 100C. At the end of the reaction period, the condensation product can then be recovered by stripping off water and unreacted reagents under reduced pressure at temperatures from about 110C. to about 200C. and preferably, from about 140C. to about 170C.
Another method for carrying out the condensation re-action is to methylolate a phenol (monomethylolation) by react-ing a phenol with an aldehyde under base catalysis at tempera-tures of from about 50C. to about 110C., and preferably from about 60C. to about 80C. The reaction mixture is then made (slightly) acidic (if not already so) and the aniline is added and condensed with the foregoing at temperaturesof from about 50C. to about 12SC., and preferably, from about 95C. to about 100C. At the end of the reaction period, the condensation product can be recovered by stripping off water and unreacted reagents under reduced pressure at temperatures from about 110 C. to about 200C. and preferably, from about 140C. to about 170C. Yet another method for carrying out the condensation reaction is to make a phenolic novolac resin using the well known acid catalyzed reaction of phenol and aldehyde. The un-recovered phenolic resin (containing water and unreacted phenol) is then made mildly acidic (if not already so) and the aromatic amine added. The final condensation is then carried out by adding further aldehyde to the foregoing mixture while being maintained at a temperature of from about 50C. to about 125C., preferably, from about 95 to about 100C. At the end of the reaction period, the condensation product can be recovered by stripping off water and unreacted reagents under reduced pres-sure at temperatures from about 110C. to about 220C. and preferably, from about 140C. to about 170C.
In general, as first prepared, the amine modified novo-lac is typically an aqueous solution or dispersion, the exact conditions and respective quantities and types of reactions in any given instance being determinative of the character of the product (including degree of advancement, color, etc.). The amine modified phenolic resin can be concentrated (and even prepared as a solid resin) and impurities such as unreacted re-actants largely removed by means of dehydration under vacuum.

~087787 As those skilled in the art appreciate, typical dehydration con-ditions are distillation under about 28 i-nches~mërcury vacuum until batch temperature reaches about 160C. though any con- ~~
venient conditions can be employed.
Yields of amine modified novolac resin typically vary from about 85 to 110% tbased on combined starting (charged) weights of aromatic amine and phenol). In general, higher aro-matic amine mol ratios, as well as higher aldehyde to phenol plus aromatic amine ratios give higher yields. Aniline-phenol-formaldehyde resins prepared as just described generally have the above-described characteristics and constitute a preferred class of amine modified phenolic resins suitable for use in the present invention.
In general, for use in the present invention, amine modified novolac resins are prepared in the form of substantially anhydrous starting materials, as explained above. "
An advantage in dehydrating a starting amine modified novolac is that the dehydration procedure (using heat and re-duced pressure as described above) typically also tends to re-move impurities from a starting resin, such as unreacted started materials, catalysts, etc.
The aromatic carbonyl-containing compound must contain at least two carbonyl-containing groups in the ortho position.
The anhydride groups, each with a valence of two, and each con-taining two carbonyl-containing groups, are always attached to adjacent carbon atoms on an aromatic ring. The compounds can contain any combination of anhydride, acid, or ester groups. A
preferred number of carbonyl-containing groups per molecule is four, such as two anhydride groups, four ester groups, or com-lOB7787 bination of any four of these carbonyl-containing groups. A
particularly preferred aromatic carbonyl containing compound is trimellitic acid anhydride. The aromatic radicals must each ~~
contain at least two carbonyl-containing groups attached to adjacent carbon atoms whereas the other carbonyl-containing groups can be on any other ring position.
In general, for use in the present invention, aromatic polycarboxylic compounds are prepared in the form of substan-tially anhydrous starting materials.
PREPARATION OF COMPOSITIONS
To make a thermoset resinous composition of this inven-tion, one takes an amine modified novolac resin as described above and an aromatic polycarboxylic compound as described above and simply mixes the two components together until a sub-stantially uniform product mixture is obtained. The relativeproportions of each are as described above.
In general, the proportion of aromatic polycarboxylic compound to amine modified novolac resin in any given thermo-settable composition is such that the composition will thermo-set when exposed to an elevated temperature, e.g., a tempera-ture of 150C. or higher. Preferably, the proportion of aro-matic polycarboxylic compound to amine modified novolac resin is such that amide, imide, and/or ester linkages can be formed at each amine hydrogen and each phenolic hydroxyl site within each amine modified novolac resin molecule. However, thermo-settability is frequently achievable by using less than all such amine hydrogen and phenolic hydroxyl sites when crosslinking with an aromatic polycarboxylic compound such as taught in this invention. Also, thermosettability is not appreciably affected, C-06-12-0430 lQ8~87 within wide limits, by using excesses of stoichiometric amounts of aromatic polycarboxylic compounds in relation to a given quantity of another modified novolac resin. During thermo-setting, it should be noted that at higher temperatures, e.g., temperatures say above 200C. or more, typically, though not necessarily, rearrangements can occur in the thermoset material which result in a higher concentration of one form of linkage as opposed to another. For example, it is tentatively theorized (and there is no intent to be bound by theory herein) that at higher temperatures, rearrangement to form imide linkages is common in a given thermoset product of this invention.
In general, the thermoset resinous compositions of this invention, owing to the initial substantially dehydrated char-acter of each of the amine modified novolac resin and of the aromatic polycarboxylic compounds, respectively, employed in these compositions, are in the form of powders which are char-acteristically free flowing.
When making a solid, thermoset composition of this in-vention, it is preferred to use an amine modified novolac resin and an aromatic polycarboxylic compound (as described above, respectively) in the form of solids which have particle si2es generally under about 100 mesh (U. S. Standard sieves). Pref-erably, particle sizes under about 50 mesh are used. The ad-mixing of one component with the other can be made in a blender, such as a so-called Waring Blender, a ball mill, or the like, although any convenient mechanical mixing means may be employed~
In the solid compositions of this invention, it will be appreciated that the ratio of amine modified novolac resin to aromatic polycarboxylic compounds is as indicated above. How-*Trade Mar~

C-06~12-0430 ever, mixtures of different amine modified novolac resins and of different aromatic polycarboxylic compounds can be employed in any given composition to enhance characteristics desired for a particular end use application as those skilled in the art will readily appreciate.
Thermosettable aromatic amine modified novolac resins in combination with aromatic polycarboxylic compounds as con-trasted to the thermoset resins of the present invention, have been disclosed in U. S. P. 3,558,559 by John R. LeBlanc. The various phenols, aromatic amines and aromatic carboxylic com-pounds that can be used in the preparation of the thermoset friction particles of the present invention are detailed com-prehensively in U. S. P. 3,558,559.

lS The friction particle of this invention may be used alone or with other friction materials known in the art. A
typical frietion element contains about 30 to 60 weight percent asbestos fiber, up to 40 weight percent other inorganic filler and abrasives, about S to 15 weight percent organic filler, in-cluding the particle of this invention, and about lS to 30 weight percent binder; all percents are by weight of total com-position. Asbestos fiber, other abrasive materials and filler materials are charged into a mixer followed by the addition of a binder, such as a novolac material. The materials are kneaded until the fiber, abrasives and any fillers are thoroughly mixed and a uniform mass is obtained. The mass is discharged from the mixer, rolled out into sheets or extruded or pressure molded and dried, after which it is ready for further processing into friction elements.

'1087787 "

The abrasives, that is, the friction imparting agents and fillers, which may be used in addition to the abrasive material disclosed and elaimed herein, within the scope of this invention include, but are not limited to brass chips, metal 5 shavings and filings, silica, talc, wood flour, chalk, clay, mica, fiber glass, felt, carbon black, graphite, metal nitrides and oxides, and ground cashew nut shell oil polymerizate.
These abrasives and fillers may be used in addition to the friction particle of this inVentiOn to achieve the particular 10 amount of bulk and coefficient of friction desired. Some con-sumer specifications specify that the friction particle should be 90% finer than 20 mesh and coarser than 100 mesh. Other consumer specifications call for coarser or finer friction particles.
The following examples are set forth to illustrate the practices of this invention to one skilled in the art and are not intended to be restrictive or limit the scope of the in-vention.
EXAMPLE A-l Preparation of Amine Modified Phenolic Novolac Resin . A mixture of 1005 grams (10.7 mols) of phenol and 99S
grams (10.7 mols) of aniline is heated to 70C. in a S-liter, 3-neck Pyrex*reaction flash that is equipped with stirrer, thermometer, reflux condenser and dropping funnel. At 70C., 26.6 grams (0.52 mol~ of 90~ strength formic acid is added and -allowed to mix. Next, over about a 2-1/2 hour period, 91S
grams (15.25 mols) of 50 weight percent aqueous formaldehyde solution is added to the reaction mixture while stirring vigor-` ously. The rèaction mixture is refluxed ror 45 minutes at about *Trade Mark r~

100C. The reaction flask is then changed over to vacuum dis-tillation conditions and vacuum slowly applied up to about 7"
Hg (temperature stabilized at about 90C.). As the temperature reached about 9SC. (with about 7" Hg vacuum), the vacuum is increased slowly to about 10" Hg. As the temperature reached about 100C., the vacuum is increased slowly to about 20" Hg.
When the temperature reached about 110C., the vacuum is in-creased slowly to 28" Hg. The temperature is then allowed to rise to 160C. with 28" Hg of vacuum while continuing to dis-till. At 160C., the distillation is stopped and the productpoured into a pan to cool. The resulting amine modified phe-nolic resin is a clear, brittle, glasslike solid at room tem-perature. The distillate has two phases; the lower layer being mostly phenol and aniline and the upper layer being mostly water. The yield of solid resin is about 88~ based on the sum of the phenol and aniline charge.
EXAMPLES A-2 THROUGH A-ll Following the same general procedure described in Ex-ample A-l, a series of amine modified phenolic resins are pre-pared from phenol~ aniline and formaldehyde. Table 1 belowdescribes each resin. EXAMPLES A-12 THROUGH A-21 Following the same general procedure described in Ex-ample A-l, a series of amine modified phenolic resins are pre-pared using various substituted phenols and aromatic amines.Table II below describes such resin.

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U~ O 1-')o C-06-12-0430 1~87 EXAMPLES B (1-9) 100 parts of phenol and 0.5 part concentrated sulfuric acid are charged to a suitable reaction vessel and heated to -~
95C. Dropwise, there is added 48 parts 50% formalin at such a rate so that the reaction exotherm is controlled and a uniform atmospheric boil is initiated. After addition of formalin is complete, the reaction mixture is heated at atmospheric reflux (100C.) for 1 hour. Then this intermediate mixture is de-; hydrated under vacuum to an end point of about 115C. at 10"
Hg vacuum. To this intermediate resin is added 30 parts of diene codimer compound mixture available commercially as "Resin Former P" from the Hess Oil and Chemical Company (described above) over a period of 30 minutes while keeping the tempera-ture at 115-125C. The temperature of the mixture is held be-tween 115 and 125C. after addition of diene codimer compound ¦ for 30 minutes. This product mixture is desolvated under vacuum to an end point of about 130C. at 28" Hg vacuum. The product is drained from the reaction vessel while hot and fluid and then allowed to solidify.
. !
The foregoing procedure is repeated using different amounts of either the diene codimer compound mixture or the - formaldehyde. The results for all examples are summarized in Table II below.

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TEST PROCEDURES
Friction particles were evaluated in friction element formulations with a Grano Friction Element Tester (GFET). The ~~
G.F.E.T. is a friction element test machine which has both the constant imput force capa~ilities of the General Motors Friction Materials Test Machine described in SAE Publication 670S10 and the constant output torque capabilities of the F.A.S.T. machine described in SAE Publication 670079. Basically, the G.F.E.T.
is a disc pad tester in which two small friction elements mounted on a rotating support are pressed against a restrained friction plate. The torque generated on the friction plate, as the friction elements move, is recorded and correlated with the normal force applied to the elements. The coefficient of fric-tion is the ratio of the generated tangential force to the normal applied force.
The G.F.E.T. can be operated in either a constant imput (constant normal force) mode or a constant output tconstant generated tangential force or torque) mode. The constant input mode is analogous to constant pedal pressure in an automotive brake, while constant output simulates constant deceleration rate., In an ideal brake system, constant input should result in constant output tand vice versa); but in real systems, fade frequently occurs and the coefficient of friction often changes as the brake temperature and history changes.
The G.F.E.T. can also be used to measure wear. By measuring specimen thickness before and after a test, wear can be measured as a function of temperature, generated torque, etc. for a given test duration. In addition, the G.F.E.T. can be used to get a rough idea of noise which may be generated *Trade Mark . ~
,:
~,.

10~7787 when brakes are applied.
A. SPecimen Preparation Two basic procedures are utilized in preparing specimens ~~
for testing in the G.F.E.T. These are the cold press pro-cess and the hot press process. In general, the cold press process is used with liquid resin systems in which the cold pressed preform has enough coherence to "stick" together during further handling. The hot press process is generally used with dry resins. In both cases, the molded specimens are post-baked to develop full strength and other proper-ties. Typical procedures for mixing, molding and post-baking speciments are presented below. Specific experiments, of course, may utilize different conditions or procedures.
1. Mixing Procedure a. Beat asbestos fibers for 1 hour in Patterson-Kelly Blender with intensifier bar.
b. Weigh out proper amount of asbestos and add to Hobart mixer.
c. Add resin to asbestos and mix 10 minutes.
d. Add friction particles and barytes and mix an additional 20 minutes.
2. Cold Press Conditions a. Charge enough material to mold to obtain re-quired density in 3/8" thick specimen.
b. Close press to 3/8" stops and hold several minutes~
c. Open press and remove preformed specimens.

~0877~

3. Hot Press Conditions a. Preheat mold to 330-340F. (or other desired temperature). ~~
b. Charge enough material to mold to obtain re-quired density in 3/8" thick specimen.
c. Mold to 3/8" stops and breathe mold about 5 times (or as necessary) in first two minutes of molding.
d. Cure 4" dia. disc mold 10 minutes.
e. Remove specimens from hot mold.
4. Post-Bake Conditions a. Cure cold press preforms under slight holding pressure (several psi) in oven at desired tem-perature. Post-bake cycle depends on resin type but generally reaches 160-220C. in about 12 hours.
b. Cure hot press discs at atm. pressure in air circulating oven. Post-bake cycles vary, but most common run to date is 12 hour cycle with linear temperature increase from 8~C. to 220C.
5. Specimen Preparation ` a. Cut post-baked discs into 3~4 x 3/4 inch ~, specimens~
b. Sand faces parallel before testing.
B. Tests , The primary tests used to evaluate the high temperature performance of the friction particles described were a constant input, continuous drag test similar to the General Motors C-l Test (described in the C-l test Procedure of the General Motors ~08~787 Technical Center, Warren, Michigan) and a continuous drag wear test. The tests are summarized as follows:
1. C-l Test This test is similar to the SAE J661a fade test except it is not limited to normal forces of 150 psi or specimen temperatures of 650F. In the C-l test, normal forces ranging from 50 psi to 200 psi are applied during a 15 minute constant input, continuous drag test. As used with the G.F.E.T., the C-l test utilizes five consecutive 15 , - 10 minute drag tests with successive normal pressures of 50, 100, 150, 200 and 50 psi. The coefficient of friction is plotted as a function of temperature at each 1 minute in-terval and wear is measured after each test. As with the J661a wear test, the C-l wear measurements are of little value since they do not hold output wor~ (torque) constant.
The C-l fade measurements, however, are very helpful in development work since they show exactly when various .~
- formulations begin to fade. Many systems do not fade until 700-800F. and would not be described fully in the 650F.
max. J661a test. The C-l test frequently reaches tempera-tures above 800F. and tests have been run above 1,000F.
2. Wear Test This test provides a constant output tor~ue measure of wear. ln the G.F.E.T. wear test, the specimen temperature is held constant (generally at 650F.) and the specimens are subjected to 200 in.-lbs. of torque while moving at 20 ft./sec. for 20 minutes.

C-06-12-0430 ~08~87 The following examples illustrate practice of the present invention:

330 grams of resin from Example A-4, 670 grams of resin from Example A-9 and 600 grams of trimellitic anhydride (TMA) are ground together through a laboratory Raymond mill (hammer mill) until essentially all of the material passes U. S. Sieve No. 140. The product is placed in an aluminum tray and heated for 1 hour~in a 500F. air-circulating oven. At the end of this .
period the material has foamed up and has the shape of a bread loaf. The cooled brittle loaf is broken up and ground to 60 - mesh and again placed in the aluminum tray and reheated for 1 hour at 500F. The dark final product is ground and sieved to 60-140 mesh and made up into a disc ~rake pad by blending 10 parts by weight of the friction particle product with 10 parts , barytes, 60 parts asbestos and 20 parts Resinox RI-4052 (an alkylated phenolic novolac resin compound available from the Monsanto Company). The disc pad formulation is molded at 335F., 200 psi for 11 minutes and then cut into test specimens. The test specimens are post baked for 12 hours in an oven programmed from 50C. to 220C. The specimens are then cooled, machined to required width and tested in a Grano Friction Element Tester ~G.F.E.T.). A control was prepared in the same manner using Cardolite N-104-40 (3 M Company) as the friction particle.
The following results were obtained in a C-l test at 200~psi constant input load.

*Trade Mark C-0~-12-0430 ~087787 Time Coefficient of Disc Temperature of Test Friction F.
(Min.) Cardolite Ex. 1 Cardolite Ex. 1 0 0.33 0.30 100 100 ~
0.28 0.41 715 675 0.09 0.53 785 970 The following wear data were obtained in a G.F.E.T. wear test run at 200 in.-lbs. output torque, 650F., 20 ft./sec., 20 minutes continuous drag:

-~ 10 Specimen Weight Specimen Thick-Friction Loss ness Loss ~- Particle (gms) (%)(ins) (%) - Cardolite 0.3640 6.40.195 5.4 Exampie 1 0.4527 7.2.0235 6.5 330 grams of resin from Example A-4, 670 grams of resin from Example A-9 and 300 grams of TMA are formulated and pro-cessed into a friction particle as described in Example 1. It is then formulated and made into a friction element by blending as described in Example 1 except 20 parts of Resinox 753 is used as the.binder instead of Resinox RI-4052. Resinox 753 is a phenol/formaldehyde novolac resin made by Monsanto Company.
Testing in the C-l and wear test as described in Example 1 gives the following results:

*Trade Mark C-l Test Time Coefficient of Disc Temperature of Test Friction ~F.
(Min.) Cardolitf . Ex. 2 Cardolite Ex. 2 0 0.26 0.28 100 100 fi 10 0.29 0.28 595 560 :` 15 0.27 0.47 810 835 . Wear Test Specimen Weight Specimen Thick- ~~
. 10 Friction Loss ness Loss ~ Particle (~ms) (%) (ins) (%) .~. _ Cardolite 0.4674 7.7 0.023 6.4 j Example 2 0.3971 6.7 0.0185 5.1 .~

~, 15 A friction particle similar to that of Example 1 is pre-pared except that benzophenone tetracarboxylic acid dianhydride (BTDA) is used instead of TMA. The friction particles are form-ulated and made into a friction element as in Example 2 and a C-l test and wear test are run with the following results:

: Time of Test Coefficient of Disc Temperature (Min.) Friction (F.) 0 0.27 100 0.25 700 lS ~.46 g45 Wear Test Specimen Weight Loss Specimen Thickness Loss (gms) (~) (ins) (~) 0.9571 119.5 0.053 1 15.0 lOB7787 A friction particle identical to Example 1 is prepared with 450 gms of TMA instead of 600 gms. The friction particles are formulated and made into friction elements as described in 5 Example 1 and a C-l and wear test is run with the following results:
~
~ C-l Test -Time of Test Coefficient of Disc Temperature 10 (Min ) Friction (F ) 0 0.29 100 0.44 745 lS 0.48 1040 Wear Test _ lS Specimen Weight Loss Specimen Thickness Loss (gms) (%) (ins) (%) 1.6099 1 30.2 0.105 1 29.0 Other Binder Resins Novolac resins are the preferred binder resins for the brake lining composition as described. However, the invention is not limited to such binder resins. Other resin binder materials for brake lining compositions are known to those skilled in the art, e.g. vulcanized rubbers, crosslinked drying oils and in particular thermosettable phenolic resole resins.

C-06-12-0430 1~87 Preparation of a Phenolic Resole Resin About 2800 grams (26.7 mols) of phenol and 2860 grams --(35.2 mols) of 37 weight percent formalin are charged to a 3 gallon stainless steel reaction kettle equipped with a horse-shoe agitator, thermometer, reflux condenser and necessary piping. The temperature is adjusted to about 35C. 25 grams ~ (0.08 mols) of barium hydroxide octohydrate dissolved in 50 r grams of hot water are added, together with 100 grams (0.69 . , mols) of hexamethylenetetramine. The batch is heated to a 65C. vacuum reflux (about 3.0 p.s.i.a.). It is maintained at 65C. for about 2-1/2 hours. At the end of the reflux time, the kettle is changed over to vacuum dehydration with the vacuum being increased slowly to about 1.5 p.s.i.a. The batch is dehyrated with the vacuum being increased to about 1.0 p.s.i.a. as the temperature rises to about 50C. Dehydration ; is continued until the resin is grindable by test (usually at about 85-90C. with 1.0 p.s.i.a. vacuum). When a sample of the resin is grindable (completely brittle at room temperature), the batch is poured into a pan to cool. A fan is used to cool the resin rapidly to room temperature. The resulting phenolic resole lump resin is an essentially clear, low melting solid at room temperature. The yield of solid resin is about 126 on the phenol charge.

About 20 parts of the resole resin of Example S was blended with 10 parts of the friction particles of Example 1, 10 parts of barytes and 60 parts of asbestos to form a disc pad formulation. The formulation was molded into a disc pad and tested as in Example 1. The tests showed that the pad had properties comparable to disc pads formulated with novolac binders. --:

_ 117 --

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a brake lining composition comprising friction particles and a resin binder therefor, wherein said improvement comprises, said friction particles comprising a thermoset re-action product of (A) an aromatic amine modified novolac resin characterized by having:
(1) a number average molecular weight of from about 200 to 1000, (2) at least two aryl moieties per molecule, the aryl nucleus of each aryl moiety containing from 6 through 10 carbon atoms each, (3) at least one divalent bridging moiety of the formula:

wherein R1 and R2 are each individually selected from the group consisting of hydrogen, lower alkyl, lower alkalene, lower haloalkyl aryl of from 6 through 12 carbon atoms and haloaryl of 6 through 12 carbon atoms, said bridging moiety having the unsatisfied valences of its carbon atom each bonded to a different one of said aryl moieties, (4) at least one >NH group per molecule, one bond of which is directly attached to one of said aryl nuclei and the other bond of which is attached to another of said aryl nuclei or to a radical R1 as defined above, (5) at least one OH group per molecule each such group being directly attached to a different one of said two aryl nuclei, (6) a percent oxygen acetyl of from about 3 to 26, and (7) a percent nitrogen acetyl of from about 3 to 26, and (B) an aromatic polycarboxylic compound of the formula:

in which R3 is an aromatic radical of three, four, five or six valences and containing from 6 to 24 carbon atoms, R4 is a monovalent hydrocarbon radical containing less than 19 carbon atoms; n is an integer of from 0 through 3; m is an integer of from 0 through 6; p is an integer of from 0 through 6; when n is 0, the sum of m+p is an integer of from 3 through 6;
when n is 1, the sum of m+p is an in-teger of from 1 through 4; when n is 2, the sum of m+p is an integer of from 0 through 2; and the sum of n and p is always at least 1, (C) the relative proportions of said amine modified resin and said aromatic poly-carboxylic compound being such that said composition is thermoset by heat said thermoset friction particles being infusible at temperatures above 700°F., being dispersed in and held in place by said binder.

2. A composition of Claim 1 wherein said aromatic poly-carboxylic compound is an ester of trimellitic anhydride.

3. A composition of Claim 1 wherein-said aromatic poly-carboxylic compound is an ester of benzophenone tetracarboxylic anhydride.

4. A composition of Claim 1 wherein said aromatic poly-carboxylic compound is an ester of pyromellitic anhydride.

5. A composition of Claim 1 wherein said resin binder comprises a thermosettable phenol-formaldehyde novolac resin.

6. A composition of Claim 1 wherein said composition contains additives, selected from the group consisting of as-bestos, fillers and abrasives or mixtures thereof.

7. In a method of forming a brake lining composition comprising the blending of a resin binder and friction particles wherein the improvement comprises, the blending of friction particles comprising a thermoset reaction product of:
(A) an aromatic amine modified novolac resin characterized by having:
(1) a number average molecular weight of from about 200 to 1000, (2) at least two aryl moieties per molecule, the aryl nucleus of each aryl moiety containing from 6 through 10 carbon atoms each, (3) at least one divalent bridging moiety of the formula:

wherein R1 and R2 are each individually selected from the group consisting of hydrogen, lower alkyl, lower alkalene, lower haloalkyl aryl of from 6 through 12 carbon atoms and haloaryl of 6 through 12 carbon atoms, said bridging moiety having the unsatisfied valences of its carbon atom each bonded to a different one of said aryl moieties, (4) at least one >NH group per molecule, one bond of which is directly attached to one of said aryl nuclei and the other bond of which is attached to another of said aryl nuclei or to a radical R1 as defined above, (5) at least one OH group per molecule each such group being directly attached to a different one of said two aryl nuclei, (6) a percent oxygen acetyl of from about 3 to 26, and (7) a percent nitrogen acetyl of from about 3 to 26, and (B) an aromatic polycarboxylic compound of the formula:

in which R3 is an aromatic radical of three, four, five or six valences and con-taining from 6 to 24 carbon atoms, R4 is a monovalent hydrocarbon radical containing less than 19 carbon atoms; n is an integer of from 0 through 3; m is an integer of from 0 through 6; p is an integer of from 0 through 6; when n is 0, the sum of m+p is an integer of from 3 through 6; when n is 1, the sum of m+p is an integer of from 1 through 4; when n is 2, the sum of m+p is an integer of from 0 through 2;
and the sum of n and p is always at least 1, (C) the relative proportions of said amine modified resin and said aromatic poly-carboxylic compound being such that said composition is thermoset by heat said thermoset friction particles being infusible at temperatures above 700°F., being dispersed in and held in place by said binder resin.

8. A method of Claim 7 wherein said aromatic poly-carboxylic compound is an ester of trimellitic anhydride.

9. A method of Claim 7 wherein said aromatic poly-carboxylic compound is an ester of benzophenone tetracarboxylic anhydride.

10. A method of Claim 7 wherein said aromatic poly-carboxylic compound is an ester of pyromellitic anhydride.

11. A method of Claim 7 wherein said resin binder com-prises a thermosettable phenol-formaldehyde novolac resin.

12. A method of Claim 7 wherein said resin binder com-prises a thermosettable phenol-formaldehyde resole resin.

13. A composition of Claim 1 wherein said resin binder comprises a thermosettable phenol-formaldehyde resole resin.

14. A composition of Claim 1 wherein said composition comprises about 15 to 30% by weight of said resin binder, about 30 to 60% of asbestos, up to about 40% of fillers and abrasives about 5 to 15% by weight of said friction particles.